Post-mortem interval (PMI) is the most important part of every medico-legal investigation as it narrow down the field of investigation. In the past decade many methods have been introduced for the precise estimation of PMI. The estimation of PMI should be highly accurate as the whole investigation depends on it. The traditional methods which were used in the beginning of the decade were bound in the time limit. Such methods like rigor mortis, livor mortis, algor mortis, decomposition etc can only provide some superficial idea about the PMI in the early death hours. But with the rising era of biochemical methods the whole face of investigation has changed and the medico-legal investigation has attained the new levels of accuracy which were never before. But all these methods now need a restart to become more rapid, sensitive and cost effective. Here the review describes the emergence of biochemical methods as an efficient tool for the determination of PMI.